We present a systematic investigation of the structural and electronic changes that occur in an Fe(0)-N2 unit (Fe(depe)2(N2); depe = 1,2-bis(diethylphosphino)ethane) upon addition exogenous Lewis acids. Addition neutral boranes, alkali metal cations, Fe2+ complex increases N-N bond activation (Δ νNN up to 172 cm-1), decreases redox potential, polarizes bond, enables -N protonation at uncommonly anodic potentials. These effects were rationalized using combined experimental theoretical studies.

A new bifunctional pincer ligand framework bearing pendent proton-responsive hydroxyl groups was prepared and metalated with Ru(II) subsequently isolated in four discrete protonation states. Stoichiometric reactions H2 HBPin showed facile E–H (E = H or BPin) activation across a Ru(II)–O bond, providing access to unusual Ru–H species strong interactions neighboring proton boron atoms. These complexes were found promote the catalytic hydroboration of ketones nitriles under mild conditions,...

Looking to the future: The decomposition in solution of a potential hydrogen-storage compound, ammonia borane (AB), was investigated by situ 11B NMR spectroscopy and ex 15N spectroscopy. reaction found be second order AB with an activation barrier (25±2) kcal mol−1. second-order kinetics have implications for use solutions containing high concentrations hydrogen storage. Supporting information this article is available on WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z802100_s.pdf...

In situ(11)B NMR monitoring, computational modeling, and external trapping studies show that selectivity extent of H(2) release in metal-catalysed dehydrogenation ammonia borane, NH(3)BH(3), are determined by coordination reactive aminoborane, NH(2)BH(2), to the metal center.

Determining the true, kinetically dominant catalytically active species, in classic benzene hydrogenation system pioneered by Maitlis and co-workers 34 years ago starting with [RhCp*Cl(2)](2) (Cp* = [η(5)-C(5)(CH(3))(5)]), has proven to be one of most challenging case studies quest distinguish single-metal-based "homogeneous" from polymetallic, "heterogeneous" catalysis. The reason, this study will show, is previous failure use proper combination of: (i) operando spectroscopy determine...

X-ray absorption fine structure (XAFS) is used to determine the of rhodium cluster present during catalyzed dehydrocoupling amine boranes under operando conditions. We show how a variety XAFS strategies can be in combination with other analytical methods differentiate homogeneous from heterogeneous systems. Analysis situ spectra using series (NH3BH3, R2NHBH3, and RNH2BH3 where R = methyl, isopropyl, tert-butyl, cyclohexyl) catalyst precursor compounds (including...

An amide-derived NNN-Ru(II) hydride complex catalyzes oxidant-free, acceptorless, and chemoselective dehydrogenation of primary secondary amines to the corresponding nitriles imines with liberation dihydrogen. The catalyst system tolerates oxidizable functionality is selective for (-CH2NH2) in presence without α-CH hydrogens.

An amide-derived <italic>N</italic>,<italic>N</italic>,<italic>N</italic>-Ru(<sc>ii</sc>) complex catalyzes the conversion of EtOH to 1-BuOH with high activity.

We present the direct and stereoretentive deuteration of primary amines using Ru-bMepi (bMepi = 1,3-(6'-methyl-2'-pyridylimino)isoindolate) complexes D2O. High deuterium incorporation occurs at α-carbon (70-99%). For α-chiral amines, complete retention stereochemistry is achieved when an electron-deficient Ru catalyst. The enantiomeric purity attributed to a high binding affinity imine intermediate with ruthenium, as well fast H/D exchange relative ligand dissociation.

The ligand 6,6′-dihydroxy terpyridine (dhtp) is presented as a bifunctional capable of directing proton transfer events with metal-coordinated substrates. Solid-state analysis Ru(II)-dhtp complex reveals directed hydrogen-bonding interactions the hydroxyl groups dhtp Ru-bound chloride ligand. utility was demonstrated by chemoselective hydrogenation ketones.

The bmpi (1,3-bis(6′-methyl-2′-pyridylimino)isoindoline) pincer Ru(II) hydride complex catalyzes base-free, acceptorless, and chemoselective dehydrogenation of alcohols with liberation dihydrogen under moderate (<120 °C) conditions. Primary diols are converted to ester lactone products high conversion efficiencies. catalyst system is remarkably selective for the oxidation secondary in presence primary alcohols.

An amide-derived N,N,N-Fe(II) complex catalyzes the hydroboration of alkenes at room temperature. Alkylation a remote site on ligand backbone was used as late-stage modification to provide more electrophilic determined by electrochemical studies. The alkylated variant, compared parent complex, olefin with an increased reaction rate and exhibits distinct regioselectivity for internal alkene hydroboration.

In this Perspective, we outline recent examples of homogeneous transition-metal hydrogen transfer catalysts for which functionality within the complex's outer coordination sphere influences outcome a reaction. Secondary-sphere groups are often applied to reactions, but their specific role during catalysis is not always well-understood. New experimental and theoretical work details complexity associated with predicting secondary-sphere interactions therefore designing improved catalysts. This...

Remarkable differences in selectivity and activity for ruthenium-catalyzed transfer hydrogenation are described that imparted by pendent OH groups. Kinetic experiments, as well the study of control complexes devoid groups, reveal groups serve to orient ketone substrate through ion pairing with an alkali metal under basic conditions. The deprotonation was found modulate electronics at center, providing a more electron rich ruthenium center. effects between metals alkoxide were highlighted...

A nonheme iron complex bearing the tris(6-phenylamino-pyridyl)methylamine (TPANHPh) ligand with appended hydrogen bond (H-bond) groups displays facile O2 reactivity to form a monomeric Fe(III)OH complex, which can release •OH via rebound carbon radical. An analogous compound without H-bonds, based on tris(6-methylpyridyl)methylamine (TPAMe), exhibits minimal reactivity, forming Fe(III)2(μ-O)(μ–OH) dimer, also reacts carbon-based radicals. The H-bonding system enables binding and activation...

The reversible transformations between ketones and alcohols via sequential hydrogenation–dehydrogenation reactions are efficiently achieved using a single precatalyst HRu(bMepi)(PPh3)2 (bMepi = 1,3-bis(6′-methyl-2′-pyridylimino)isoindolate). catalytic mechanism of mediated acceptorless alcohol dehydrogenation (AAD) has been investigated by series kinetic isotopic labeling studies, isolation intermediates, evaluation Ru(b4Rpi)(PPh3)2Cl (R H, Me, Cl, OMe, OH) complexes. Two limiting scenarios...

A new series of bifunctional Ru complexes with pendent Lewis acidic boranes were prepared by late-stage modification an active hydrogen-transfer catalyst. The appended modulate the reactivity a metal hydride as well catalytic hydrogenations. After installing auxiliary groups, become multifunctional and catalyze cis-selective hydrogenation alkynes higher rates, conversions, selectivities compared unmodified

Ruthenium–terpyridine complexes appended with secondary amines impart hydride stability and recyclability toward catalytic dehydrogenative alcohol oxidation to carboxylates.

Incorporation of two 9-borabicyclo[3.3.1]nonyl substituents within the secondary coordination sphere a pincer-based Fe(II) complex provides Lewis acidic sites capable binding 1 or 2 equiv N2H4. Reduction 1:1 Fe:N2H4 species affords rare Fe(NH2)2 in which amido ligands are stabilized through interactions with appended boranes. The NH2 units can be released as NH3 upon protonation and exchanged exogenous

The difluoromethyl group (R–CF2H) imparts desirable pharmacokinetic properties to drug molecules and is commonly targeted as a terminal functional that not amenable further modification. Deprotonation of widely available Ar–CF2H starting materials expose nucleophilic Ar–CF2– synthons represents an unexplored, yet promising route construct benzylic Ar–CF2–R linkages. Here we show the combination Brønsted superbase with weak Lewis acid enables deprotonation groups capture reactive fragments....

A copper complex featuring a proton-responsive tripodal ligand reduces nitrite<italic>via</italic>a proton/electron transfer process, which parallels nitrite reductase.

A fluoroform-derived borazine CF3- transfer reagent is used to effect rapid nucleophilic reactions in the absence of additives, within minutes at 25 °C. Inorganic electrophiles spanning seven groups periodic table can be trifluoromethylated high yield, including transition metals for catalytic trifluoromethylation. Organic included (hetero)arenes, enabling C-H and C-X trifluoromethylation reactions. Mechanistic analysis supports a dissociative mechanism transfer, cation modification afforded...

A detailed mechanistic analysis of the acceptorless double dehydrogenation primary amines to form nitriles by HRu(bMepi)(PPh3)2 (1, bMepi = 1,3-bis(6′-methyl-2′-pyridylimino)isoindolate) is presented. The presence ortho-CH3 substituents on critical for amine dehydrogenation, and no catalysis was observed with HRu(bpi)(PPh3)2 (1-bpi, bpi 1,3-bis(2′-pyridylimino)isoindolate). Outer-sphere, inner-sphere, hemilabile pathways were evaluated through ligand substitution kinetic studies, catalyst...

Abstract 6,6′′‐Bis(2,4,6‐trimethylanilido)terpyridine (H 2 Tpy NMes ) was prepared as a rigid, tridentate pincer ligand containing pendent anilines hydrogen bond donor groups in the secondary coordination sphere. The geometry of )copper(I)‐halide (Cl, Br and I) complexes is dictated by strength NH–halide bond. Cu I Cl II are nearly isostructural, former presenting highly unusual square‐planar about . geometric constraints provided interactions reminiscent blue copper proteins where...

The trans-Fe(DMeOPrPE)2Cl2 complex (where DMeOPrPE = 1,2-bis(bis(methoxypropyl)phosphino)ethane) undergoes a series of reactions that involve the activation both H2 and N2 to produce ammonia hydrazine. A Leigh-type cycle was employed achieve laboratory fixation dinitrogen at room temperature pressure utilizing as reductant.